Effects of drought on the effectiveness of Phalaris arundinacea and Impatiens glandulifera in building up soil aggregates – a microcosm approach

Near natural floodplain ecosystems are not only stressed by frequent inundations over a year but also by periodical droughts in summer due to their reduced water retention capacity. To maintain floodplain habitats as biodiversity hotspots, a stable soil structure is required. Soil ecosystem engineers (EEs) such as plants and earthworms, who are known to build up soil macro-aggregates, have to tolerate rough conditions while they colonize these habitats. EEs¿ effectiveness on soil aggregation under periodical drought conditions has never been investigated so far. To simulate different drought intensities, a microcosm approach under controlled conditions will be set up. Soil sediments, plants and earthworms will be collected in a restored floodplain river section and incubated 8 weeks at 15°C under different soil moisture conditions. Plant resistance to drought will be assessed through leaf water potential and transpiration monitoring as well as through innovative measurements of plant resistance to embolism. This approach will help to increase the understanding of how EEs behave under periodical stress conditions.